Electric implements may be carried or pulled by work vehicles. For example, three or more electrically powered cutting reels may be carried by fairway mowers, greens mowers, trim mowers and other turf care products. Electric seeding equipment pulled by tractors may include multiple seeding row units having electric motors.
Electric power for these implements may be supplied by an alternator or generator driven directly by an internal combustion engine, or by an energy storage device or fuel cell charged by the alternator. Electric motors for the implements may include brush-less permanent magnet motors, commutated electric motors, or other electric motors.
With a typical alternator, particularly a Lundell-type alternator having an output rectifier, if more current is demanded than the alternator can supply, the alternator's output voltage may collapse, yet the current may not correspondingly increase. The alternator's electrical power output does not stay at the maximum available, but drops precipitously.
As a result, if current demand by multiple electrically powered implement motors is very high, approaching or exceeding the capacity of the power generating component, the electrical power may be significantly lower due to a sharp voltage drop. Once the voltage drops too far, it can be insufficient to power other electrical functions on the work vehicle, resulting in a condition commonly referred to as “brownout.” Other power generating devices such as permanent magnet alternators, electrochemical batteries, DC machines and others suffer from overload problems of a type similar to the above. For example, electrochemical cells will undergo voltage collapse under high load conditions, particularly when the battery is highly discharged.
If the total electrical implement load reaches or exceeds the maximum allowable load, the implements may stall or fault and stop functioning. For the above reasons, it is desired to provide an electric implement power management system that reduces the peak power demands on an alternator. It is desired to provide an electric implement power management system that reduces peak power demands before total electric implement load reaches an overload condition.